1. Field of the Invention
The present invention relates to a semiconductor device manufacturing apparatus and an operating method thereof in which a process is applied to an object to be processed, for example, a reduction process is applied to a metal oxide, or a cleaning process is applied to the inside of a processing container, by supplying a vapor of a corrosive liquid source to the processing container.
2. Description of the Related Art
There is a case where a process is performed by using a vapor of a corrosive liquid source in a semiconductor device manufacturing apparatus which provides a processing container so as to apply a process to a substrate. As an example, there is a process which reduces a surface oxide layer of copper wiring by using an organic acid. This process is described in detail. When copper multi-layer wiring is formed, in order to connect a lower copper layer to an upper copper layer, a via hole is formed in a dielectric interlayer, and an electrode is formed by filling the via hole with copper. The surface of the lower copper wiring is oxidized by the atmosphere after forming the via hole. That is, an oxide layer is formed on the surface of the lower copper wiring. However, when the via hole is filled by the copper electrode in this state, the resistance value between the copper wiring and the copper electrode becomes large. In Patent Document 1, in order to decrease the resistance value, a processing chamber is provided in which chamber a vaporized carboxylic acid such as a formic acid is supplied and the copper oxide is reduced.
A container which stores, for example, the formic acid is generally formed of a stainless steel (SUS) having high corrosion resistance. If quartz or resin is used for the container, it is difficult to form an airtight connecting structure between the container and a pipe used for supplying the formic acid, because the pipe is generally made of metal.
However, when the formic acid is stored in the stainless steel container, a metal component in the stainless steel is dissolved in the formic acid. A metal component such as iron in the stainless steel is ionized (oxidized) by an electrochemical reaction due to corrosion potential. That is, when an oxidization reaction (M→Mn++ne−) of a metal M is studied, the equilibrium potential E of the metal M is shown in Equation (1) (Nernst Equation).E=E0+RT/nF·ln a   (1)
where R is the gas constant (8.314 J/mol K), T is the absolute temperature, “n” is the number of concerned electrons, F is the Faraday constant (96500 C/mol), “a” is the activity of the metal ion Mn+, and the E0 is the reference electrode potential (equilibrium potential when a metal is immersed in a solution of “a”=1). When the metal potential is greater than the equilibrium potential E, corrosion theoretically occurs due to the progress of the ionization of the metal. In the above system, the electric potential of the stainless steel is greater than the equilibrium potential E. The value of the equilibrium potential E is calculated by using an acceptable metal impurity concentration (approximately 10−6 to 10−8; approximately 100 to 1 ppb) in the formic acid liquid as the value of “a”.
As described above, when a metal component in the stainless steel is dissolved in the formic acid liquid, a part of the metal component is included in a vapor of the formic acid liquid and the part of the metal component is permeated into a semiconductor wafer in the processing container. Consequently, metal contamination occurs in the semiconductor wafer. The characteristics of the semiconductor wafer are greatly affected by even a small amount of the metal contamination. Consequently, the yield of a semiconductor device may be decreased by the metal contamination. When the processing container is cleaned, the vapor of a corrosive liquid source is also used for cleaning the processing container. In this case, a metal component is absorbed on a table, and when a semiconductor wafer is put on the table, the metal component is absorbed on the backside surface of the semiconductor wafer. With this, the metal component is absorbed by another semiconductor device manufacturing apparatus and the metal contamination occurs in the semiconductor wafer.
[Patent Document 1] Japanese Laid-Open Patent Application No. 2003-218198, Paragraph 0018